Multiple polishing heads with cross-zone pressure element distributions for cmp

ABSTRACT

Various embodiments of the present disclosure are directed towards a chemical mechanical polishing (CMP) system including a first CMP head and a second CMP head. The first CMP head is configured to retain a workpiece and comprises a first plurality of pressure elements disposed across a first pressure control plate. The second CMP head is configured to retain the workpiece. The second CMP head comprises a second plurality of pressure elements disposed across a second pressure control plate. A distribution of the first plurality of pressure elements across the first pressure control plate is different from a distribution of the second plurality of pressure elements across the second pressure control plate.

BACKGROUND

The semiconductor integrated circuit (IC) industry has experienced rapid growth. Technological advances in IC materials and design have produced generations of ICs where each generation has smaller and more complex circuits than the previous generation. However, these advances have increased the complexity of processing and manufacturing ICs and, for these advances to be realized, developments in IC processing and manufacturing occur. For example, planarization technology, such as a chemical mechanical polishing (CMP) process, has been implemented to planarize a wafer or one or more layers of features over the wafer in order to reduce a thickness of the wafer, remove excessive materials from the processed surface, or prepare the processed surface for a subsequent manufacturing process.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It is noted that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.

FIGS. 1A-1C illustrates some embodiments of various views of a chemical mechanical polishing (CMP) system comprising a first CMP head and a second CMP head that respectively have a plurality of pressure elements.

FIGS. 2A-2B illustrates some embodiments of top views of a workpiece having a plurality of pressure elements arranged proximate to the workpiece.

FIG. 3A illustrates some embodiments of a plurality of graphs which set forth removal rates of the first CMP head and the second CMP head during operation of the CMP system of FIGS. 1A-1C.

FIG. 3B illustrates some embodiments of a layout view of a workpiece having a plurality of pressure elements arranged proximate to a workpiece.

FIG. 3C illustrates some embodiments of a layout view of a workpiece having a plurality of concentric pressure zones disposed across a workpiece.

FIG. 4 illustrates some embodiments of a block diagram of a polishing apparatus having a CMP head.

FIG. 5 illustrates some embodiments of a cross-sectional view of a plurality of CMP heads.

FIG. 6 illustrates some embodiments of a cross-sectional view of a plurality of CMP heads according to some alternative embodiments of the plurality of CMP heads of FIG. 5.

FIG. 7 illustrates some embodiments of a block diagram of a CMP system.

FIG. 8 illustrates some embodiments of a method for polishing a to-be-polished surface of a workpiece using a plurality of CMP heads.

FIGS. 9-14 illustrate cross-sectional views of some embodiments of structures illustrating the method of FIG. 8.

DETAILED DESCRIPTION

The present disclosure provides many different embodiments, or examples, for implementing different features of this disclosure. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly.

Moreover, “first”, “second”, “third”, etc. may be used herein for ease of description to distinguish between different elements of a figure or a series of figures. “first”, “second”, “third”, etc. are not intended to be descriptive of the corresponding element, but rather are merely generic identifiers. For example, “a first dielectric layer” described in connection with a first figure may not necessarily correspond to a “first dielectric layer” described in connection with some embodiments, but rather may correspond to a “second dielectric layer” in other embodiments.

According to some chemical mechanical polishing (CMP) systems, a platen is covered with a polishing pad and is configured to rotate the polishing pad. A polishing head is arranged over the polishing pad, and is configured to support and rotate a workpiece. The polishing head comprises comprises a plurality of pressure elements disposed across concentric pressure zones of the polishing head. The plurality of pressure elements are configured to press corresponding concentric surfaces on a front-side of the workpiece into the polishing pad with varying force. These concentric surfaces on the front-side of the workpiece may be called to-be-polished workpiece surfaces. The pressure of the plurality of pressure elements may be adjust in order to achieve a desired workpiece thickness. A slurry distribution system comprises one or more nozzles arranged over the polishing pad, and is configured to provide a slurry to the polishing pad through the nozzle(s). The slurry comprises chemical and abrasive components. Due to the pressing force and the slurry, the to-be-polished surfaces of the workpiece undergoes chemical and mechanical polishing.

A challenge with the foregoing CMP system is that the plurality of pressure elements may not evenly distribute pressure across a corresponding concentric pressure zone. This, in part, may be due to processing tool limitations of the pressure elements and results in a variation in thickness across the to-be-polished surfaces of the workpiece that correspond to the concentric pressure zones. For example, a pressure exerted by a first pressure element of the CMP head may be greater in a center region of a first concentric pressure zone than in a peripheral region of the first concentric pressure zone. Thus, areas of the front-side of the workpiece between adjacent concentric pressure zones may be subjected to more or less polishing depending on the applied pressure, such that those areas of the workpiece have a different workpiece thickness that is not desired. This can result in the workpiece having poor workpiece thickness uniformity and a significantly large total thickness variation (TTV) (e.g., greater than about 0.35 micrometers (um)). The significantly large TTV may cause issues in proceeding processing steps such as under-etching, poor bonding interfaces, etc. that may result in device failure and/or change electrical properties of electronics disposed on/over the workpiece.

Various embodiments of the present application are directed towards an improved CMP system with an associated method for polishing a workpiece to improve workpiece thickness uniformity. The CMP system comprises a first CMP head configured to perform a first CMP process on the workpiece and a second CMP head configured to perform a second CMP process on the workpiece. The first CMP head comprises a first plurality of pressure elements distributed across a first plurality of concentric pressure zones on a first pressure control plate. Further, the second CMP head comprises a second plurality of pressure elements distributed across a second plurality of concentric pressure zones on a second pressure control plate. The distribution of the first plurality of pressure elements across the first pressure control plate is different from the distribution of the second plurality of pressure elements across the second pressure control plate.

During operation of the CMP system, the first CMP head performs the first CMP process on the workpiece to achieve a desired workpiece thickness. Accordingly, areas of the workpiece between adjacent concentric pressure zones in the first plurality of concentric pressure zones may be subject to more or less polishing depending on applied pressure. These areas of the workpiece have a different workpiece thickness that is not desired, such that the workpiece has a significantly large TTV (e.g., greater than about 0.35 um) after the first CMP process. Subsequently, the second CMP head performs the second CMP process on the workpiece. By virtue of the second plurality of pressure elements having a different distribution than the first plurality of pressure elements, the second CMP head is configured to compensate for the undesired workpiece thickness achieved during the first CMP process. For example, each pressure element in the second plurality of pressure elements may continuously extend over an area between adjacent pressure elements of the first plurality of pressure elements. As a result, the second CMP head may compensate for the undesired workpiece thickness in the areas of the workpiece between the adjacent concentric pressure zones in the first plurality of concentric pressure zones. This, in part, results in the workpiece having a more accurate planarization, such that the TTV of the workpiece after the second CMP process is substantially small (e.g., less than about 0.3 um).

FIGS. 1A-1C illustrates some embodiments of various views of a chemical mechanical polishing (CMP) system 100 comprising a first CMP head 106 and a second CMP head 114. FIG. 1A illustrates a schematic view of some embodiments of the CMP system 100. FIG. 1B illustrates a cross-sectional view of some embodiments of the first CMP head 106. FIG. 1C illustrates a cross-sectional view of some embodiments of the second CMP head 114.

The CMP system 100 includes a first polishing apparatus 102 comprising a first platen 104 and the first CMP head 106. The first CMP head 106 is attached to a first end of a first support arm 108 that extends over the first platen 104 and a second end of the first support arm 108 is anchored at a point adjacent to the first platen 104 (e.g., anchored to a housing of the CMP system 100). The first CMP head 106 is, for example, configured to perform a first CMP process on a workpiece 105 (e.g., a semiconductor wafer) when the workpiece 105 is positioned on the first platen 104. In such embodiments, the workpiece 105 is positioned between the first CMP head 106 and the first platen 104 during the first CMP process. Further, a second polishing apparatus 110 is laterally adjacent to the first polishing apparatus 102 and comprises a second platen 112 and the second CMP head 114. The second CMP head 114 is attached to a first end of a second support arm 116 that extends over the second platen 112 and a second end of the second support arm 116 is anchored at a point adjacent to the second platen 112 (e.g., anchored to a housing of the CMP system 100). The second CMP head is, for example, configured to perform a second CMP process on the workpiece 105 when the workpiece 105 is positioned on the second platen 112. In such embodiments, the workpiece 105 is position between the second CMP head 114 and the second platen 112 during the second CMP process. In some embodiments, the first and second support arms 108, 116 may be, for example, telescoping. The first polishing apparatus 102 and the second polishing apparatus 110 define a polishing station 118. In some embodiments, any number of polishing stations may be provided and/or the polishing station 118 may comprise any number of polishing apparatuses. For example, a second polishing station 119 may be disposed adjacent to the polishing station 118. In various embodiments, the first and second CMP heads 106, 114 of the second polishing station 119 may be different from the first and second CMP heads 106, 114 of the polishing station 118.

With reference to FIG. 1B, the first CMP head 106 includes an upper housing 138, an annular retaining ring 136, a first pressure control plate 139, and a first plurality of pressure elements 140 a-e disposed across the first pressure control plate 139. Further, a polishing pad 107 is disposed on the first platen 104 between the first CMP head 106 and the first platen 104. The first CMP head 106 is configured to hold the workpiece 105 between sidewalls of the annular retaining ring 136. The first plurality of pressure elements 140 a-e are disposed over the workpiece 105 and are configured to exert independent amounts of suction or pressure onto corresponding concentric regions of a back-side of the workpiece 105. This suction or pressure applies force to the workpiece 105 such that a front-side of the workpiece 105 is pressed against the polishing pad 107. The force with which the workpiece 105 is pressed against the polishing pad 107 will control a remove rate of materials disposed on the front-side of the workpiece 105. Further, the first plurality of pressure elements 140 a-e are respectively disposed in a first plurality of concentric pressure zones A1-A5 across the first pressure control plate 139. For example, a first pressure element 140 a of the first CMP head 106 is disposed in a concentric pressure zone A1, a second pressure element 140 b of the first CMP head 106 is disposed in a concentric pressure zone A2 that laterally surrounds the first pressure element 140 a of the first CMP head 106, a third pressure element 140 c is disposed in a concentric pressure zone A3 that laterally surrounds the second pressure element 140 b of the first CMP head 106, and so on. The first plurality of concentric pressure zones A1-A5 correspond to concentric surfaces on a front-side of the workpiece 105 that may be polished during a corresponding CMP process. These concentric surfaces on the front-side of the workpiece 105 may be referred to as to-be-polished workpiece surfaces.

With reference to FIG. 1C, the second CMP head 114 comprises an upper housing 138, an annular retaining ring 136, a second pressure control plate 142, and a second plurality of pressure elements 144 a-e disposed across the second pressure control plate 142. Further, a polishing pad 107 is disposed on the second platen 112 between the second CMP head 114 and the second platen 112. The second CMP head 114 is configured to hold the workpiece 105 between sidewalls of the annular retaining ring 136. The second plurality of pressure elements 144 a-e are disposed over the workpiece 105 and are configured to exert independent amounts of suction or pressure onto corresponding concentric regions of the back-side of the workpiece 105. Further, the second plurality of pressure elements 144 a-e are respectively disposed in a second plurality of concentric pressure zones B1-B5 across the second pressure control plate 142. For example, a first pressure element 144 a of the second CMP head 114 is disposed in a concentric pressure zone B1, a second pressure element 144 b of the second CMP head 114 is disposed in a concentric pressure zone A2 that laterally surrounds the first pressure element 144 a of the second CMP head 114, a third pressure element 144 c is disposed in a concentric pressure zone A3 that laterally surrounds the second pressure element 144 b of the second CMP head 114, and so on. The second plurality of concentric pressure zones B1-B5 correspond to concentric surfaces on the front-side of the workpiece 105 that may be polished during a corresponding CMP process.

In various embodiments, a diameter of the first pressure control plate 139 is equal to a diameter of the second pressure control plate 142, such that the first plurality of pressure elements 140 a-e are distributed across a same area as the second plurality of pressure elements 144 a-e. In further embodiments, a distribution of the first plurality of pressure elements 140 a-e across the first pressure control plate 139 is different from a distribution of the second plurality of pressure elements 144 a-e across the second pressure control plate 142.

In some embodiments, during operation of the CMP system 100, the first CMP head 106 is configured to perform the first CMP process on the workpiece 105 such that the first plurality of pressure elements 140 a-e each exert force on the back-side of the workpiece 105. The pressure of the first plurality of pressure elements 140 a-e may be adjusted in order to achieve a desired workpiece thickness. For example, the pressure may be selected in order to exert enough force by the first plurality of pressure elements 140 a-e to cause the workpiece 105 to be forced down on the polishing pad 107 and planarized to a predetermined degree. In various embodiments, due to processing tool limitations, the pressure elements in the first plurality of pressure elements 140 a-e may not evenly distribute pressure across the corresponding concentric pressure zones A1-A5. For example, a pressure exerted by the first pressure element 140 a of the first CMP head 106 may be greater in a center region of the concentric pressure zone A1 than in a peripheral region of the concentric pressure zone A1 (e.g., near the circumferential edge of the first pressure element 140 a of the first CMP head 106). Thus, areas of the front-side of the workpiece 105 between adjacent concentric pressure zones A1-A5 may be subjected to more or less polishing depending on the applied pressure, such that those areas of the workpiece 105 have a different workpiece thickness that is not desired. This may result in the workpiece 105 having a significantly large TTV (e.g., greater than about 0.35 um) after the first CMP process.

Accordingly, in some embodiments, to avoid the undesired workpiece thickness, the second CMP head 114 is configured to perform the second CMP process after performing the first CMP process. During the second CMP process, the second plurality of pressure elements 144 a-e each exert force on the back-side of the workpiece 105. In some embodiments, the pressure of the second plurality of pressure elements 144 a-e is adjusted in order to achieve the desired workpiece thickness and may be configured to compensate for the undesired workpiece thickness achieved during the first CMP process. For example, pressure elements in the second plurality of pressure elements 144 a-e may continuously extend over an area between adjacent pressure elements of the first plurality of pressure elements 140 a-e, such that the second plurality of pressure elements 144 a-e may compensate for the undesired workpiece thickness in the areas of the front-side of the workpiece 105 between the adjacent concentric pressure zones A1-A5. This, in part, results in the workpiece 105 having a more accurate planarization, such that the TTV of the workpiece 105 after the second CMP process is substantially small (e.g., less than about 0.3 um). Thus, by virtue of the distribution of the second plurality of pressure elements 144 a-e being different from the distribution of the first plurality of pressure elements 140 a-e a uniform planarization may be achieved such that the workpiece 105 has the substantially small TTV.

Further, the first plurality of pressure elements 140 a-e respectively have a first plurality of widths 141 a-e. In some embodiments, the first pressure element 140 a of the first CMP head 106 may be configured as a circular pressure element, and second, third, fourth, and fifth pressure elements 140 b-e of the first CMP head 106 may respectively be configured as an annular pressure element (i.e., a ring-shaped pressure element). Thus, a first width 141 a of the first plurality of widths 141 a-e may, for example, correspond to a diameter of the first pressure element 140 a of the first CMP head 106. Further, second, third, fourth, and fifth widths 141 b-e of the first plurality of widths 141 a-e may, for example, correspond to an annular ring width of the second, third, fourth, and fifth pressure elements 140 b-e of the first CMP head 106, respectively. In various embodiments, the second, third, fourth, and fifth widths 141 b-e of the first plurality of widths 141 a-e may be equal to one another. In yet further embodiments, a radius of the first pressure element 140 a of the first CMP head 106 may be equal to the second, third, fourth, and fifth widths 141 b-e, respectively. In some embodiments, a center of the first pressure control plate 139 may be aligned with a center of the workpiece 105 during the first CMP process. In further embodiments, an inner radius of the second pressure element 140 b of the first CMP head 106 is disposed along a circumferential edge of the first pressure element 140 a of the first CMP head 106, an inner radius of the third pressure element 140 c of the first CMP head 106 is disposed along a circumferential edge of the second pressure element 140 b of the first CMP head 106, and so on.

In addition, the second plurality of pressure elements 144 a-e respectively have a second plurality of widths 145 a-e. In some embodiments, the first pressure element 144 a of the second CMP head 144 may be configured as a circular pressure element, and second, third, fourth, and fifth pressure elements 144 b-e of the second CMP head 114 may respectively be configured as an annular pressure element (i.e., a ring-shaped pressure element). Thus, a first width 145 a of the second plurality of widths 145 a-e may, for example, correspond to a diameter of the first pressure element 144 a of the second CMP head 114. Further, second, third, fourth, and fifth widths 145 b-e of the second plurality of widths 145 a-e may, for example, correspond to an annular ring width of the second, third, fourth, and fifth pressure elements 144 b-e of the second CMP head 114, respectively. In various embodiments, the second, third, fourth, and fifth widths 145 b-e of the second plurality of widths 145 a-e may be different from one another. In yet further embodiments, a center of the second pressure control plate 142 may be aligned with the center of the workpiece 105 during the second CMP process. In further embodiments, an inner radius of the second pressure element 144 b of the second CMP head 114 is disposed along a circumferential edge of the first pressure element 144 a of the second CMP head 114, an inner radius of the third pressure element 144 c of the second CMP head 114 is disposed along a circumferential edge of the second pressure element 144 b of the second CMP head 114, and so on.

In some embodiments, the distribution of the first plurality of pressure elements 140 a-e across the first pressure control plate 139 is different from the distribution of the second plurality of pressure elements 144 a-e across the second pressure control plate 142. In such embodiments, the first plurality of widths 141 a-e are different from corresponding widths in the second plurality of widths 145 a-e, respectively. For example, the first width 141 a of the first pressure element 140 a of the first CMP head 106 is different from the first width 145 a of the first pressure element 144 a of the second CMP head 114 (e.g., the first width 141 a is less than the first width 145 a), the second width 141 b of the second pressure element 140 b of the first CMP head 106 is different from the second width 145 b of the second pressure element 144 b of the second CMP head 114 (e.g., the second width 141 b is greater than the second width 145 b), and so on.

In further embodiments, the pressure elements of the first and second plurality of pressure elements 140 a-e, 144 a-e may each be or comprise, for example, a fluid-filled bladder arranged in a corresponding concentric pressure zone A1-A5, B1-B5. A pressure of each fluid-filled bladder controls a downward force applied to the workpiece 105, and may be controlled by, for example, a pump driven by a motor of the CMP system, where the controller 134 is configured to control the pump and motor. In yet further embodiments, the pressure elements of the first and second plurality of pressure elements 140 a-e, 144 a-e may, for example, be implemented by a motor of a drive system configured to directly apply force to the workpiece 105. In various embodiments, the pressure elements of the first and second plurality of pressure elements 140 a-e, 144 a-e may each be or comprise a concentric chamber arranged in a corresponding concentric pressure zone A1-A5, B1-B5. In such embodiments, a pressure applied by each concentric chamber may, for example, by controlled by a pump driven by a motor of the CMP system.

Referring back to FIG. 1A, the CMP system 100 further comprises a surface measurement apparatus 120 configured to measure one or more parameters of the workpiece 105 such as, for example, thickness, polishing uniformity, or other parameters associated with a surface of the workpiece 105. For example, the surface measurement apparatus 120 is configured to detect a thickness, evenness, planarity, and/or roughness of the surface of the workpiece 105 before, during, or after a corresponding CMP process. For example, lack of uniformity on the surface of the workpiece 105, and an interface of various materials associated with the CMP process may be monitored by the surface measurement apparatus 120. The surface measurement apparatus 120 may, for example be configured to provide optical, electrical, thermal, pressure, and/or acoustical sensing. The surface measurement apparatus 120 may be associated with the first CMP head 106 and/or the second CMP head 114. The surface measurement apparatus 120, for example, may be configured to detect vibrations, motor feedback, or temperature before, during, and/or after a corresponding CMP process. In yet further embodiments, the surface measurement apparatus 120 may be configured to report the one or more parameters of the workpiece 105 in real-time to a controller 134, in which the controller 134 may adjust parameters (e.g., pressure settings) of the first and/or second CMP heads 106, 114 based on the one or more parameters of the workpiece 105 (e.g., based on a measured planarity of the workpiece 105). In various embodiments, the surface measurement apparatus 120 may be disposed on and/or within the first and second platens 104, 112.

In some embodiments, the controller 134 may be configured to adjust pressures of the first plurality of pressure elements 140 a-e during the first CMP process and adjust pressures of the second plurality of pressure elements 144 a-e during the second CMP process according to the measurements of the surface measurement apparatus 120. For example, if a to-be-polished workpiece surface of the workpiece 105 is relatively high, then a pressure of the corresponding pressure element can be increased relative to neighboring pressure elements. Conversely, if the to-be-polished workpiece surface of the workpiece 105 is relatively low, the pressure of the corresponding pressure element can be decreased relative to neighboring pressure elements. Thus, the pressures for each pressure element 140 a-e, 144 a-e can be independently varied in a continuous and ongoing manner to tailor their respective polish rates during a corresponding CMP process, thereby providing a uniform planarization. In yet further embodiments, the controller 134 may be configured to adjust pressures of the second plurality of pressure elements 144 a-e during the second CMP process based on measurements of the surface measurement apparatus 120 taken during and/or after the first CMP process (e.g., based on a planarity of the to-be-polished workpiece surface during and/or after the first CMP process). This, in part, facilitates the workpiece 105 having the substantially small TTV (e.g., less than about 0.3 um).

Further, a loading apparatus 124 is disposed next to the polishing station 118. The loading apparatus 124 is configured to transport the workpiece 105 between one of a plurality of front opening unified pods (FOUPs) 122 and a transport apparatus 126. The transport apparatus 126 is disposed laterally adjacent to the first polishing apparatus 102 and the second polishing apparatus 110, where the transport apparatus 126 is configured to transport the workpiece 105 between the first polishing apparatus 102 and the second polishing apparatus 110. For example, the transport apparatus 126 may transport the workpiece 105 to the first polishing apparatus 102 such that the first CMP head 106 may perform the first CMP process on the workpiece 105. After the first CMP process, the transport apparatus 126 may transport the workpiece 105 to the second polishing apparatus 110 such that the second CMP head 114 may perform the second CMP process on the workpiece 105.

In some embodiments, the transport apparatus 126 comprises a wafer cart 132 and a robot 128. The robot 128 is, for example, configured to selectively transport the workpiece 105 between two or more of the first polishing apparatus 102, the second polishing apparatus 110, and/or other polishing apparatus(es) (not shown). Further, the robot 128 is, for example, operably coupled to a track 130, where the robot 128 is configured to translate along the track 130 between the first polishing apparatus 102, the second polishing apparatus 110, and/or the other polishing apparatus(es). In addition, the robot 128 may be configured to move the workpiece 105 from the loading apparatus 124, the first polishing apparatus 102, the second polishing apparatus 110, and/or the other polishing apparatus(es) to the wafer cart 132. In some embodiments, the wafer cart 132 has a drive mechanism such as rollers, gears, belts, conveyors, or magnets that may move the workpiece 105 between the various assemblies in the CMP system 100. In addition, the first and/or second CMP heads 106, 114 may each be configured to move the workpiece 105 between each other and/or to the transport apparatus 126 by way of the first and/or second support arms 108, 116.

The controller 134 is configured to control the first polishing apparatus 102, the second polishing apparatus 110, the transport apparatus 126, and/or the loading apparatus 124. For example, the controller 134 is configured to direct the loading apparatus 124 to transfer the workpiece 105 from the plurality of FOUPs 122 to the transport apparatus 126. Further, the controller 134 is configured to direct the robot 128 to selectively transport the workpiece 105 to the first polishing apparatus 102 and/or the second polishing apparatus 110. Furthermore, the controller 134 is configured to adjust parameters of the first CMP head 106 and/or the second CMP head 114 based on the one or more parameters of the workpiece 105 provided by the surface measurement apparatus 120.

FIG. 2A illustrates some embodiments of a top view of a workpiece 105 with a first plurality of pressure elements 140 a-e arranged proximate to the workpiece 105. In some embodiments, the first plurality of pressure elements 140 a-e correspond to the pressure elements of the first CMP head (106 of FIGS. 1A-1C). In further embodiments, the first plurality of pressure elements 140 a-e are disposed across the first plurality of concentric pressure zones A1-A5. In further embodiments, the first plurality of pressure elements 140 a-e may be configured as concentric pressure elements that are concentric with respect to one another and/or are each concentric with respect to a center point 105 c of the workpiece 105. In yet further embodiments, a circumferential edge of the fifth pressure element 140 e of the first plurality of pressure elements 140 a-e is aligned with a circumferential edge 105 e of the workpiece 105. Further, a radius R of the workpiece 105 is defined from the center point 105 c of the workpiece 105 to the circumferential edge 105 e of the workpiece 105. It will be appreciated that although FIG. 2A illustrates five pressure elements and five concentric pressure zones, any number of concentric pressure zones and pressure elements may be disposed across the workpiece 105.

FIG. 2B illustrates some embodiments of a top view of the workpiece 105 with a second plurality of pressure elements 144 a-e arranged proximate to the workpiece 105. In some embodiments, the second plurality of pressure elements 140 a-e correspond to the pressure elements of the second CMP head (114 of FIGS. 1A-1C). In further embodiments, the second plurality of pressure elements 144 a-e are disposed across the second plurality of concentric pressure zones B1-B5. In further embodiments, the second plurality of pressure elements 144 a-e may be configured as concentric pressure elements that are concentric with respect to one another and/or are each concentric with respect to the center point 105 c of the workpiece 105. In yet further embodiments, a circumferential edge of the fifth pressure element 144 e of the second plurality of pressure elements 144 a-e is aligned with a circumferential edge 105 e of the workpiece 105. It will be appreciated that although FIG. 2B illustrates five pressure elements and five concentric pressure zones, any number of concentric pressure zones and pressure elements may be disposed across the workpiece 105.

FIG. 3A illustrates some embodiments of a cross-section view of the first CMP head 106 and the second CMP head 114, and a plurality of graphs 302-306 which set forth removal rates of the first CMP head 106 and the second CMP head 114 during operation of the CMP system 100 of FIGS. 1A-1C. In some embodiments, the y-axis of the plurality of graphs 302-306 corresponds to a normalized removal rate of materials from a workpiece during a corresponding polishing process and the x-axis of the plurality of graphs 302-306 corresponds to a distance from a center (105 c of FIG. 2A or 2B) of the workpiece (105 of FIG. 2A or 2B).

A first removal rate graph 302 illustrates some embodiments of removal rate values across the first plurality of concentric pressure zones A1-A5 during a CMP process performed by the first CMP head 106. The x-axis of the first removal rate graph 302 is aligned with a center of the first concentric pressure zone A1, a center of the first pressure element 140 a of the first CMP head 106, and/or a center of the workpiece. A first upper curve 308 depicts an upper bound of a removal rate of materials from to-be-polished surfaces of the workpiece that correspond to the first plurality of concentric pressure zones A1-A5. A first lower curve 310 depicts a lower bound of a removal rate of materials from the to-be-polished surfaces of the workpiece that correspond to the first plurality of concentric pressure zones A1-A5. A first horizontal line 309 depicts a normalized removal rate of, for example, about one. In some embodiments, the first upper curve 308 may correspond to the removal rate of materials from the to-be-polished surfaces of the workpiece when a pressure exerted by each pressure element in the first plurality of pressure elements 140 a-e is, for example, about +20 hectopascals (hPa), or another suitable value. In further embodiments, the first lower curve 310 may correspond to the removal rate of materials from the to-be-polished surfaces of the workpiece when the pressure exerted by each pressure element in the first plurality of pressure elements 140 a-e is, for example about −20 hPa, or another suitable value. Thus, in some embodiments, the pressure exerted by each pressure element in the first plurality of pressure elements 140 a-e may, for example, be within a range of about −20 to +20 hPa. It will be appreciated that the first plurality of pressure elements 140 a-e exerting other pressure values is within the scope of the disclosure. Therefore, a removal rate across the of the first plurality of concentric pressure zones A1-A5 may be adjusted between the first upper curve 308 and the first lower curve 310 by adjusting a pressure exerted by the first plurality of pressure elements 140 a-e during the CMP process.

In some embodiments, the first upper curve 308 may continuously decrease from a center of a width of a corresponding concentric pressure zone A1-A5 to an outer edge and/or an inner edge of the corresponding concentric pressure zone A1-A5. In further embodiments, the first lower curve 310 may continuously increase from the center of the width of a corresponding concentric pressure zone A1-A5 to the outer edge and/or the inner edge of the corresponding concentric pressure zone A1-A5. For example, when a pressure exerted by the first pressure element 140 a is at a maximum value (e.g., +20 hPa), then the removal rate within the first concentric pressure zone A1 may decrease from a center of the first concentric pressure zone A1 to a first horizontal line 320 a, where the first horizontal line 320 a is aligned with an outer edge of the first concentric pressure zone A1. Thus, a removal rate value during the first CMP process may fluctuate across each concentric pressure zone A1-A5 even as a pressure exerted by a corresponding pressure element in the first plurality of pressure elements 140 a-e remains constant. This, in part, may be due to processing tool limitations of the pressure elements and can result in a variation in thickness across the to-be-polished surfaces of the workpiece, especially at areas between adjacent concentric pressure zones A1-A5, where exerted pressure by a corresponding pressure element is not easily controlled. For example, the first horizontal line 320 a is disposed at a junction between an outer edge of the first concentric pressure zone A1 and an inner edge of the second concentric pressure zone A2. In some embodiments, due to the processing tool limitations of the pressure elements, even as a pressure exerted by the first pressure element 140 a and the second pressure element 140 b is at a maximum value (e.g., +20 hPa), a normalized removal rate at the junction between the first and second concentric pressure zones A1-A2 is, for example, about one. Conversely, in such embodiments, the normalized removal rate at the center of the width of the first and second pressure elements 140 a-140 b is at a maximum value. This results in poor workpiece thickness uniformity at areas between adjacent to-be-polished surfaces of the workpiece that correspond to areas between adjacent concentric pressure zones A1-A5.

A second removal rate graph 304 illustrates some embodiments of removal rate values across the second plurality of concentric pressure zones B1-B5 during a CMP process performed by the second CMP head 114. A second upper curve 312 depicts an upper bound of a removal rate of materials from to-be-polished surfaces of the workpiece that correspond to the second plurality of concentric pressure zones B1-B5. A second lower curve 314 depicts a lower bound of a removal rate of materials from the to-be-polished surfaces of the workpiece that correspond to the second plurality of concentric pressure zones B1-B5. A first horizontal line 309 depicts a normalized removal rate of, for example, about one. In some embodiments, the second upper curve 312 may correspond to the removal rate of materials from the to-be-polished surfaces of the workpiece when a pressure exerted by each pressure element in the second plurality of pressure elements 144 a-e is, for example, about +20 hPa, or another suitable value. In further embodiments, the second lower curve 314 may correspond to the removal rate of materials from the to-be-polished surfaces of the workpiece when the pressure exerted by each pressure element in the second plurality of pressure elements 144 a-e is, for example about −20 hPa, or another suitable value. Thus, in some embodiments, the pressure exerted by each pressure element in the second plurality of pressure elements 144 a-e may, for example, be within a range of about −20 to +20 hPa. It will be appreciated that the second plurality of pressure elements 144 a-e exerting other pressure values is within the scope of the disclosure. Therefore, a removal rate across the of the second plurality of concentric pressure zones B1-B5 may be adjusted between the second upper curve 312 and the second lower curve 314 by adjusting a pressure exerted by the second plurality of pressure elements 144 a-e during the CMP process.

In some embodiments, the second upper curve 312 may continuously decrease from a center of a width of a corresponding concentric pressure zone B1-B5 to an outer edge and/or an inner edge of the corresponding concentric pressure zone B1-B5. In further embodiments, the second lower curve 314 may continuously increase from the center of the width of a corresponding concentric pressure zone B1-B5 to the outer edge and/or the inner edge of the corresponding concentric pressure zone B1-B5. For example, when a pressure exerted by the first pressure element 144 a is at a maximum value (e.g., +20 hPa), then the removal rate within the first concentric pressure zone B1 may decrease from a center of the first concentric pressure zone B1 to a second horizontal line 320 b, where the second horizontal line 320 b is aligned with an outer edge of the second concentric pressure zone B1. Thus, a removal rate value during the CMP process performed by the second CMP head 114 may fluctuate across each concentric pressure zone B1-B5 even as a pressure exerted by a corresponding pressure element in the second plurality of pressure elements 144 a-e remains constant.

A third removal rate graph 306 illustrates some embodiments of removal rate values across a workpiece surface during a multi-CMP head polishing process that includes performing a first CMP process by the first CMP head 106 and subsequently performing a second CMP process by the second CMP head 114. In some embodiments, during the multi-CMP head polishing process, the removal rate and/or removal profile of materials from the surface of the workpiece by the first CMP head 106 may destructively combine with the removal rate and/or removal materials from the surface of the workpiece by the second CMP head 114. This results in a formation of a third plurality of concentric pressure zones 322 a-i disposed across the surface of the workpiece. In some embodiments, the third plurality of concentric pressure zones 322 a-i may correspond to a plurality of to-be-polished surfaces of the workpiece. Further, a pressure exerted on each of the concentric pressure zones in the third plurality of concentric pressure zones 322 a-i corresponds to a summation of the pressure exerted by the first plurality of pressure elements 140 a-e during the first CMP process and the pressure exerted by the second plurality of pressure elements 144 a-e during the second CMP process.

In some embodiments, pressures exerted by the second plurality of pressure elements 144 a-e are based on pressures exerted by the first plurality of pressure elements 140 a-e during the first CMP process and/or based on a measured planarity of the to-be-polished surfaces of the workpiece after performing the first CMP process. The pressures exerted by the second plurality of pressure elements 144 a-e may be configured to compensate for an undesired thickness achieved by the first CMP process. In such embodiments, removal rates and/or a removal profile achieved by the first plurality of pressure elements 140 a-e may deconstructively combine with the removal rates and/or removal profile achieved by the second plurality of pressure elements 144 a-e. For example, a third upper curve 316 may correspond to an upper bound of a removal rate of materials from to-be-polished surfaces of the workpiece that correspond to the third plurality of concentric pressure zones 322 a-i after performing the multi-CMP head polishing process. In some embodiments, the third upper curve 316 may correspond to a summation of the first upper curve 308 of the first removal rate graph 302 and the second lower curve 314 of the second removal rate graph 304. Further, a third lower curve 318 may correspond to a lower bound of a removal rate of materials from the to-be-polished surfaces of the workpiece that correspond to the third plurality of concentric pressure zones 322 a-i after performing the multi-CMP head polishing process. In further embodiments, the third lower curve 318 may correspond to a summation of the first lower curve 310 of the first removal rate graph 302 and the second upper curve 312 of the second removal rate graph 304.

In further embodiments, the second plurality of pressure elements 144 a-d respectively laterally extend past a circumferential edge of a corresponding pressure element in the first plurality of pressure elements 140 a-d in corresponding outer regions 324 a-d. For example, the first pressure element 144 a of the second CMP head 114 extends outwardly past a circumferential edge of the first pressure element 140 a of the first CMP head 106 in a first outer region 324 a, the second pressure element 144 b of the second CMP head 144 extends outwardly past a circumferential edge of the second pressure element 140 b of the first CMP head 106 in a second outer region 324 b, an so on. Thus, the pressure elements within the second plurality of pressure elements 144 a-d respectively continuously extend past a corresponding region between adjacent pressure elements in the first plurality of pressure elements 140 a-e. For example, the first pressure element 144 a of the second CMP head 144 continuously extends past a region between the first and second pressure elements 140 a-b within the first outer region 324 a. In some embodiments, an inner or an outer edge of a concentric pressure zone in the third plurality of concentric pressure zones 322 a-i that extends laterally into the plurality outer region 324 a-d is disposed at a midpoint of the corresponding outer region 324 a-d. For example, an outer edge of the first concentric pressure zone 322 a is disposed at a midpoint of the first outer region 324 a.

Accordingly, a distribution of the first plurality of pressure elements 140 a-e across the workpiece is different from the distribution of the second plurality of pressure elements 144 a-e across the workpiece. This, in part, facilitates the second CMP head 114 compensating for an undesired thickness achieved in a peripheral region of each concentric pressure zone A1-A5 after performing the first CMP process. By virtue of the difference between the distributions of the first and second plurality of pressure elements 140 a-e, 144 a-e across the workpiece, a fluctuation of the removal rate value across each concentric pressure zone in the third plurality of concentric pressure zones 322 a-i may be reduced. This results in the workpiece having a more accurate planarization, such that a TTV of the workpiece after the second CMP process is substantially small (e.g., less than about 0.3 um). Further, by performing the multi-CMP head polishing process, a number of concentric pressure zones in the third plurality of concentric pressure zones 322 a-i is greater than the number of pressure elements in the first CMP head 106 or the second CMP head 114. Because the removal rate may be controlled individually in each of the concentric pressure zones 322 a-i, a more accurate planarization process may be performed on the workpiece.

FIG. 3B illustrates some embodiments of a layout view of a workpiece 105 with a plurality of pressure elements arranged proximate to the workpiece 105. For example, FIG. 3B represents the layout of pressure elements from a first CMP head (106 of FIG. 3A) overlying the workpiece 105 and the layout pressure elements from a second CMP head (114 of FIG. 3A) overlying the workpiece 105. In some embodiments, the concentric circles 326 correspond to inner and/or outer edges of pressure elements within the first plurality of pressure elements (140 a-e of FIG. 3A), and the concentric circles 328 correspond to inner and/or outer edges of pressure elements within the second plurality of pressure elements (144 a-e of FIG. 3A). The outer regions 324 a-d of the concentric circles 328 correspond to areas of the second plurality of pressure elements (144 a-e of FIG. 3A) that laterally extend past an outer edge of a corresponding pressure element in the first plurality of pressure elements (140 a-d of FIG. 3A).

FIG. 3C illustrates some embodiments of a layout view of a workpiece 105 with a plurality of concentric pressure zones disposed across the workpiece 105. In some embodiments, the concentric circles 330 corresponds to inner and/or outer edges of the third plurality of concentric pressure zones 322 a-i of FIG. 3A.

FIG. 4 illustrates some embodiments of a block diagram of a polishing apparatus 400 comprising a CMP head 408 disposed over a platen 402.

The polishing apparatus 400 further includes a polishing pad 404, a slurry arm 406, and a conditioning disk 410. In some embodiments, the polishing apparatus 400 may be configured to process workpieces (e.g., wafers) (not shown) that have a diameter of about 200 micrometers (mm), 300 mm, 450 mm, or another suitable value. The CMP head 408 is configured to contain the workpiece during a CMP process such that the workpiece is disposed between the CMP head 408 and the polishing pad 404. A controller 134 is configured to control components of the polishing apparatus 400 during the CMP process. In some embodiments, the controller 134 comprises an operating routine 417 and a feedback path 416. In various embodiments, the operating routine 417 comprises a real-time surface profile analyzer 436 and a multi-zone pressure controller 440, and the feedback path 416 comprises a memory 428 and a CMP controller 414.

In some embodiments, prior to workpiece planarization, the slurry arm 406 dispenses slurry 411, which contains abrasive slurry particles, onto a polishing surface 412 of the polishing pad 404. The CMP controller 414 is configured to rotate the platen 402 and polishing pad 404 (e.g., via a platen spindle 418) about a polishing pad axis 420, as shown by a first angular velocity arrow 422. The CMP controller 414 may be configured to perform the rotation by virtue of a motor assembly (not shown). As the polishing pad 404 rotates, the conditioning disk 410 (which can be pivoted via a scan arm 424 and rotated about a disk axis 444) traverses over the polishing pad 404 such that a conditioning surface 426 of the conditioning disk 410 is in fictional engagement with the polishing surface 412 of the polishing pad 404. In such embodiments, the conditioning disk 410 scratches or “roughs up” the polishing surface 412 continuously during polishing to facilitate consist and uniform planarization of the workpiece. The CMP controller 414 is further configured to concurrently rotate the workpiece housed within the CMP head 408 about a wafer axis 421 (e.g., via a CMP head spindle 430), as shown by a second angular velocity arrow 432. While this dual-rotation occurs (e.g., as illustrated by the first and second angular velocity arrows 422, 432), the workpiece is pressed into the slurry 411 and the polishing surface 412 within a down-force applied by the CMP head 408. For example, the down-force applied by the CMP head 408 may be applied by a plurality of pressure elements (e.g., the first plurality of pressure elements 140 a-e or the second plurality of pressure elements 144 a-e of FIGS. 1A-1C). The combination of the abrasive slurry 411, the dual-rotation, and the down-force planarizes a front-side of the workpiece until an endpoint for the CMP process is reached.

In some embodiments, during the CMP process, the surface measurement apparatus 120 is configured to measure surface condition(s) of the polishing pad 404, the conditioning disk 410, and/or the workpiece in real-time. For example, the surface measurement apparatus 120 may be configured to measure planarity of respective to-be-polished surfaces of the workpiece. Further, as the platen 402 (e.g., to which the surface measurement apparatus 120 is mounted) and the CMP head 408 undergo the dual-rotation, the surface measurement apparatus 120 traces a path 434 that traverses the to-be-polished surfaces of the workpiece. Thus, as the platen 402 and the CMP head 408 rotate with respect to one another during the CMP process, the surface measurement apparatus 120 naturally passes over the respective to-be-polished surfaces in time, and can continuously monitor heights of theses surfaces as it passes thereover.

Further, the feedback path 416 operably couples the surface measurement apparatus 120 to the CMP controller 414 and the operating routine 417. The memory 428 is configured to store measurements from the surface measurement apparatus 120 and instructions of the operating routine 417. The real-time surface profile analyzer 436 of the operating routine 417 analyzes the planarity of the to-be-polished workpiece surfaces as measured by the surface measurement apparatus 120. Based on the planarity (or lack thereof) for the respective to-be polished surfaces of the workpiece, the multi-zone pressure controller 440 can change pressures, by way of the CMP controller 414, for the respective pressure control elements, which are proximate to the respective to-be-polished surfaces of the workpiece. Because a removal rate (e.g., a CMP polishing rate) of the CMP process is proportional to pressure, this surface-by-surface pressure control scheme facilitates accurate planarization of the workpiece. Thus, the pressures for each pressure element can be independently varied in a continuous and ongoing manner to tailor their respective removal rate during the CMP process, thereby providing a uniform planarization.

In some embodiments, a first polishing apparatus (102 of FIG. 1A) and a second polishing apparatus (110 of FIG. 1A) may respectively be configured as the polishing apparatus 400, where the CMP head 408 of the first polishing apparatus (102 of FIG. 1A) is configured as the first CMP head 106 of FIG. 1B and the CMP head 408 of the second polishing apparatus (110 of FIG. 1A) is configured as the second CMP head 114 of FIG. 1C. In such embodiments, the operating routine 417 and the feedback path 416 are operably coupled to both the first and second polishing apparatuses (102, 110 of FIG. 1A), such that the operating routine 417 and the feedback path 416 are configured to control the first and second polishing apparatuses (102, 110 of FIG. 1A) as illustrated and/or described above. In addition, the controller 134 is configured to perform a first CMP process by virtue of the CMP head 408 of the first polishing apparatus (102 of FIG. 1A), and subsequently perform a second CMP process by virtue of the CMP head 408 of the second polishing apparatus (110 of FIG. 1A). In such embodiments, measurements (e.g., measurements of planarity) of the surface measurement apparatus 120 taken during and/or after the first CMP process may be stored in the memory 428, and the multi-zone pressure controller 440 may adjust pressures of pressure elements (e.g., 144 a-e of FIG. 1C) in the CMP head 408 of the second polishing apparatus (110 of FIG. 1A) during the second CMP process according to the measurements stored in the memory 428 from the first CMP process.

FIG. 5 illustrates some embodiments of a cross-sectional view of a plurality of CMP heads. The plurality of CMP heads includes a first CMP head 106, a second CMP head 114, a third CMP head 502, and a fourth CMP head 510. In some embodiments, the first, second, third, and fourth CMP heads 106, 114, 502, 510 may each be disposed in a polishing apparatus as illustrated and/or described in FIG. 4. In such embodiments, the polishing apparatuses may be disposed in a CMP system as illustrated and/or described in FIG. 1A. For example, the first and second CMP heads 106, 114 may be disposed in the polishing system (118 of FIG. 1A) and the third and fourth CMP heads 502, 510 may be disposed in the second polishing system (119 of FIG. 1A).

The first CMP head 106 comprises a first plurality of pressure elements 140 a-e respectively disposed in the first plurality of concentric pressure zones A1-A5 across the first pressure control plate 139. The second CMP head 114 comprises a second plurality of pressure elements 144 a-e respectively disposed in the second plurality of concentric pressure zones B1-BS across the second pressure control plate 142. The third CMP head 502 comprises a third plurality of pressure elements 506 a-e respectively disposed in a third plurality of concentric pressure zones C1-C5 across a third pressure control plate 504. Further, the fourth CMP head 510 comprises a fourth plurality of pressure elements 514 a-e respectively disposed in a fourth plurality of concentric pressure zones D1-D5 across a fourth pressure control plate 512. In some embodiments, the first, second, third, and fourth CMP heads 106, 114, 502, 510 may each comprise an annular retaining ring 136 and an upper housing 138, and may be attached to a corresponding support arm (not shown) as illustrated and/or described in FIGS. 1A-1C. In some embodiments, a diameter of the first pressure control plate 139, a diameter of the second pressure control plate 142, a diameter of the third pressure control plate 504, and a diameter of the fourth pressure control plate 512 are respectively equal to one another, such that the first, second, third, and fourth plurality of pressure elements 140 a-e, 144 a-e, 506 a-e, 514 a-e are respectively distributed across a same area.

Further, the first plurality of pressure elements 140 a-e respectively have a first plurality of widths 141 a-e, the second plurality of pressure elements 144 a-e respectively have a second plurality of widths 145 a-e, the third plurality of pressure elements 506 a-e respectively have a third plurality of widths 508 a-e, and the fourth plurality of pressure elements 514 a-e respectively have a fourth plurality of widths 516 a-e. In some embodiments, the first, second, third, and fourth plurality of pressure elements 140 a-e, 144 a-e, 506 a-e, 514 a-e respectively have different distributions across the corresponding pressure control plate. In such embodiments, the first, second, third, and fourth plurality of widths 141 a-e, 145 a-e, 508 a-e, 516 a-e are respectively different from each other. For example, a first width 141 a of the first pressure element 140 a of the first CMP head 106, a first width 145 a of the first pressure element 144 a of the second CMP head 114, a first width 508 a of a first pressure element 506 a of the third CMP head 502, and a first width 516 a of a first pressure element 514 a of the fourth CMP head 510 are respectively different from one another, and so on.

In various embodiments, during operation of a CMP system comprising the plurality of CMP heads, the first CMP head 106 is configured to perform a first CMP process on a workpiece (e.g., 105 of FIGS. 1A-1C) (not shown). Subsequently, the second CMP head 114 is configured to perform a second CMP process on the workpiece, the third CMP head 502 is configured to perform a third CMP process on the workpiece, and/or the fourth CMP head 510 is configured to perform a fourth CMP process on the workpiece. By virtue of the first, second, third, and fourth plurality of pressure elements 140 a-e, 144 a-e, 506 a-e, 514 a-e respectively having different distributions across the corresponding pressure plates, a pressure exerted by each pressure element of the plurality of CMP heads may be adjusted to achieve a desired wafer thickness and may be configured to compensate for an undesired wafer thickness achieved during a previous CMP process. For example, the pressure elements 144 a-e of the second CMP head 114 may compensate for the undesired wafer thickness at a region between the adjacent pressure elements in the first plurality of pressure elements 140 a-e (as illustrated and/or described in FIG. 3A). Thus, the removal rate and/or removal profile of materials from the to-be-polished surface of the workpiece by each of the first CMP head 106, the second CMP head 114, the third CMP head 502, and the fourth CMP head 510 may be configured to increase planarization of the workpiece, such that the TTV of the workpiece after the fourth CMP process is substantially small (e.g., less than about 0.3 um).

In yet further embodiments, the first CMP head 106, the second CMP head 114, the third CMP head 502, and the fourth CMP head 510 may each have a same number of pressure elements. It will be appreciated that although FIG. 5 illustrates each CMP head having five pressure elements and five concentric pressure zones, any number of concentric pressure zones and pressure elements may be disposed across a corresponding CMP head. In yet further embodiments, first, second, third, and fourth plurality of pressure elements 140 a-e, 144 a-e, 506 a-e, 514 a-e may, for example, respectively be or comprise a fluid-filled bladder, a motor of a drive system, a concentric chamber, or the like as described in FIGS. 1A-1C.

In some embodiments, during operation of the CMP system comprising the plurality of CMP heads, the first CMP head 106 performs a first CMP process on the workpiece, and then the second CMP head 114 performs a second CMP process on the workpiece. In further embodiments, during operation of the CMP system, the first CMP head 106 performs a first CMP process on the workpiece, the second CMP head 114 performs a second CMP process on the workpiece, and then the third CMP head 502 performs a third CMP process on the workpiece. In yet further embodiments, during operation of the CMP system, the first CMP head 106 performs a first CMP process on the workpiece, the second CMP head 114 performs a second CMP process on the workpiece, the third CMP head 502 performs a third CMP process on the workpiece, and then the fourth CMP head 510 performs a fourth CMP process on the workpiece.

FIG. 6 illustrates some embodiments of a cross-sectional view of a plurality of CMP heads according to some alternative embodiments of the plurality of CMP heads of FIG. 5, in which the plurality of CMP heads may, for example, have a different number of pressure elements.

In some embodiments, the first CMP head 106 comprises a first plurality of pressure elements 140 a-e respectively disposed in the first plurality of concentric pressure zones A1-A5 across the first pressure control plate 139. The second CMP head 114 comprises a second plurality of pressure elements 144 a-g respectively disposed in a second plurality of concentric pressure zones B1-B7 across the second pressure control plate 142. In various embodiments, a number of pressure elements in the second plurality of pressure elements 144 a-g is greater than a number of pressure elements in the first plurality of pressure elements 140 a-e. The third CMP head 502 comprises a third plurality of pressure elements 506 a-h respectively disposed in a third plurality of concentric pressure zones C1-C8 across the third pressure control plate 504. In some embodiments, a number of pressure elements in the third plurality of pressure elements 506 a-h is greater than the number of pressure elements in the first and/or second plurality of pressure elements 140 a-e, 144 a-g. Further, the fourth CMP head 510 comprises a fourth plurality of pressure elements 514 a-h respectively disposed in a fourth plurality of concentric pressure zones D1-D8 across the fourth pressure control plate 512. In further embodiments, a number of pressure elements in the fourth plurality of pressure elements 514 a-h is greater than the number of pressure elements in the first and/or second plurality of pressure elements 140 a-e, 144 a-g. In some embodiments, the first, second, third, and fourth CMP heads 106, 114, 502, 510 may each comprise an annular retaining ring 136 and an upper housing 138, and may be attached to a support arm (not shown) as illustrated and/or described in FIGS. 1A-1C. In some embodiments, a diameter of the first pressure control plate 139, a diameter of the second pressure control plate 142, a diameter of the third pressure control plate 504, and a diameter of the fourth pressure control plate 512 are respectively equal to one another, such that the first, second, third, and fourth plurality of pressure elements 140 a-e, 144 a-g, 506 a-h, 514 a-h are respectively distributed across a same area.

Further, the first plurality of pressure elements 140 a-e respectively have a first plurality of widths 141 a-e, the second plurality of pressure elements 144 a-g respectively have a second plurality of widths 145 a-g, the third plurality of pressure elements 506 a-h respectively have a third plurality of widths 508 a-h, and the fourth plurality of pressure elements 514 a-h respectively have a fourth plurality of widths 516 a-h. In some embodiments, the first, second, third, and fourth plurality of pressure elements 140 a-e, 144 a-g, 506 a-h, 514 a-h respectively have different distributions across the corresponding pressure control plate. In such embodiments, the first, second, third, and fourth plurality of widths 141 a-e, 145 a-g, 508 a-h, 516 a-h are respectively different from each other. In yet further embodiments, a maximum width in the fourth plurality of pressure elements 514 a-h is less than a minimum width in the first plurality of widths 141 a-e.

By virtue of the first, second, third, and fourth plurality of pressure elements 140 a-e, 144 a-g, 506 a-h, 514 a-h respectively having different distributions across the corresponding pressure plates, a pressure exerted by each pressure element of the plurality of CMP heads may be adjusted to achieve a desired wafer thickness and may be configured to compensate for an undesired wafer thickness achieved during a previous CMP process. For example, the pressure elements 144 a-g of the second CMP head 114 may compensate for the undesired wafer thickness at a region between the adjacent pressure elements in the first plurality of pressure elements 140 a-e (as illustrated and/or described in FIG. 3A).

In yet further embodiments, the first CMP head 106, the second CMP head 114, the third CMP head 502, and/or the fourth CMP head 510 may have a different number of pressure elements. It will be appreciated that although FIG. 6 illustrates the first CMP head 106 having five pressure elements and five concentric pressure zones, the second CMP head 114 having seven pressure elements and seven concentric pressure zones, the third CMP head 502 having eight pressure elements and eight concentric pressure zones, and the fourth CMP head 510 having eight pressure elements and eight concentric pressure zones, any number of concentric pressure zones and pressure elements may be disposed across a corresponding CMP head.

In some embodiments, during operation of a CMP system comprising the plurality of CMP heads, the first CMP head 106 performs a first CMP process on the workpiece, and then the second CMP head 114 performs a second CMP process on the workpiece. In further embodiments, during operation of the CMP system, the first CMP head 106 performs a first CMP process on the workpiece, the second CMP head 114 performs a second CMP process on the workpiece, and then the third CMP head 502 performs a third CMP process on the workpiece. In yet further embodiments, during operation of the CMP system, the first CMP head 106 performs a first CMP process on the workpiece, the second CMP head 114 performs a second CMP process on the workpiece, the third CMP head 502 performs a third CMP process on the workpiece, and then the fourth CMP head 510 performs a fourth CMP process on the workpiece. In various embodiments, during operation of the CMP system, the first CMP head 106 performs a first CMP process on the workpiece, the fourth CMP head 510 performs a second CMP process on the workpiece, the first CMP head 106 performs a third CMP process on the workpiece, and then the fourth CMP head 510 performs a fourth CMP process on the workpiece.

FIG. 7 illustrates some embodiments of a block diagram of a CMP system 700. The CMP system includes a first polishing apparatus 702, a second polishing apparatus 704, and a planarity tool 708. In some embodiments, during use of the CMP system 700, the first polishing apparatus 702 is applied to a workpiece 706, and the second polishing apparatus 704 is subsequently applied to the first planarized workpiece 706′, to achieve a substantially planar workpiece 706″. Advantageously, by performing the second planarization after the first planarization, the second planarization minimally impacts the throughput of the first polishing apparatus 702.

A planarity tool 708 is associated with the first polishing apparatus 702 and/or the second polishing apparatus 704. In some embodiments, the planarity tool 708 may be independent of the first polishing apparatus 702 and/or the second polishing apparatus 704. In yet further embodiments, the planarity tool 708 may include a surface measurement apparatus (e.g., 120 of FIGS. 1A and/or 4) that is integrated with the first polishing apparatus 702 and/or the second polishing apparatus 704. The planarity tool 708 is configured to measure the planarity of a to-be-polished surface of the workpiece 706 and the first planarized workpiece 706′, so the locations of uneven regions (i.e., regions with an undesired workpiece thickness) on the to-be-polished surface can be identified. The planarity tool 708 may, for example, measure the planarity of the workpiece 706 and the first planarized workpiece 706′ using optical, electrical, thermal, pressure, and/or acoustical sensing.

In further embodiments, during use of the CMP system 700, the planarity tool 708 measures the planarity of the workpiece 706 in real time during the first planarization performed on the workpiece 706 by the first polishing apparatus 702. In some embodiments, parameters (e.g., a pressure exerted) of each pressure element in the first polishing apparatus 702 may be adjusted in real time based on the real time planarity measurement of the planarity tool 708 during the first planarization. Subsequently, the second polishing apparatus 704 is configured to perform the second planarization on the first planarized workpiece 706′. The planarity tool 708 measures the planarity of the first planarized workpiece 706′ in real time during the second planarization process. In some embodiments, parameters (e.g., a pressure exerted) of each pressure element in the second polishing apparatus 704 may be adjusted in real time based on the real time planarity measurement of the planarity tool 708 during the second planarization. Also, during use of the CMP system 700, in some embodiments, the planarity tool 708 measures the planarity of the second planarized workpiece 706″ after the second planarization. In such embodiments, the second planarization may be repeated until the planarity of the second planarized workpiece 706″ meets predetermined criteria. For example, the second planarization may be repeated until the second planarized workpiece 706″ has less than a predetermined number of uneven regions and/or has a TTV less than a predetermined TTV value (e.g., less than about 0.30 um). In further embodiments, each repeated second planarization may include using another CMP head different from CMP heads used in the first or second planarization, and/or using a same CMP head used in the first or second planarization. Further, the planarity measurements may be used for any repeated planarization.

In some embodiments, the first polishing apparatus 702 may, for example, be configured as the polishing apparatus 400 of FIG. 4 and/or may comprise the first CMP head 106 of FIG. 1B, 3A, 5, or 6. In yet further embodiments, the second polishing apparatus may, for example, be configured as the polishing apparatus 400 of FIG. 4 and/or may comprise the second CMP head 114 of FIG. 1B, 3A, 5 or 6, the third CMP head 502 of FIG. 5 or 6, and/or the fourth CMP head 510 of FIG. 5 or 6.

FIG. 8 illustrates a flowchart providing some embodiments of a method 800 of planarizing a to-be-polished surface of a workpiece using a first CMP head and a second CMP that have different distributions of pressure elements across the corresponding CMP head. Although the method 800 is illustrated and/or described as a series of acts or events, it will be appreciated that the method is not limited to the illustrated ordering or acts. Thus, in some embodiments, the acts may be carried out in different orders than illustrated, and/or may be carried out concurrently. Further, in some embodiments, the illustrated acts or events may be subdivided into multiple acts or events, which may be carried out at separate times or concurrently with other acts or sub-acts. In some embodiments, some illustrated acts or events may be omitted, and other un-illustrated acts or events may be included.

At act 802, a workpiece is provided. The workpiece may be, for example, a semiconductor wafer (e.g., a crystalline silicon substrate, a silicon-on-insulator (SOI) substrate, or the like) supporting electronic circuits under manufacture.

At act 804, in some embodiments, a thinning process is performed on the front-side surface of the workpiece. The thinning process may, for example, include performing a mechanical grinding process, or another suitable thinning process.

At act 806, a first chemical mechanical polishing (CMP) process is performed on the front-side surface of the workpiece. The first CMP process is performed with a first CMP head having a first distribution of a first plurality of pressure elements across the first CMP head. The first CMP process may be performed by, for example, the first CMP head 106 of FIG. 1A-1B, 3A, 5, or 6. In some embodiments, the first CMP process may include performing the acts 808 and 810.

At act 808, the planarity of the front-side surface of the work piece is measured. In some embodiments, the planarity of the front-side surface of the workpiece is measured to identify locations of uneven regions (i.e., regions with an undesired workpiece thickness) on the front-side surface of the work piece. The planarity of the front-side surface may, for example, be measured by an optical sensor, an electrical sensor, a thermal sensor, a pressure sensor, and/or an acoustical sensor. Further, the planarity of the front-side surface may, for example, be measured before, and/or in real time during, the first CMP process.

At act 810, parameter(s) of the first plurality of pressure elements is/are adjusted according to the planarity measurement of act 808. In some embodiments, the parameter(s) of the first plurality of pressure elements is/are adjusted in real time during the first CMP process based on the real time measurement of the planarity of the front-side surface of the work piece. For example, a pressure exerted by each pressure element in the first plurality of pressure elements may be adjusted in real time according to the real time measurement of the planarity of the front-side surface of the work piece during the first CMP process.

At act 812, a second CMP process is performed on the front-side surface of the workpiece. The second CMP process is performed with a second CMP head having a second distribution of a second plurality of pressure elements across the second CMP head, where the second distribution is different from the first distribution. In further embodiments, the second CMP process is performed based on the measured planarity of the front-side surface (e.g., based on the identified locations of the uneven regions). For example, an initial pressure exerted by each pressure element in the second plurality of pressure elements during the second CMP process may be based on the measured planarity of the front-side surface of the workpiece after and/or during the first CMP process. The second CMP process may be performed by, for example, the second CMP head 114 of FIG. 1A, 1C, 3A, 5, or 6. In various embodiments, the second CMP process may include performing the acts 814 and 816.

At act 814, the planarity of the front-side surface of the work piece is measured. In some embodiments, the planarity of the front-side surface of the workpiece is measured to identify locations of remaining uneven regions (i.e., regions with an undesired workpiece thickness) on the front-side surface of the work piece. The planarity of the front-side surface may, for example, be measured by an optical sensor, an electrical sensor, a thermal sensor, a pressure sensor, and/or an acoustical sensor. Further, the planarity of the front-side surface may, for example, be measured before, and/or in real time during, the second CMP process.

At act 816, parameter(s) of the second plurality of pressure elements is/are adjusted according to the planarity measurement of act 814. In some embodiments, the parameter(s) of the second plurality of pressure elements is/are adjusted in real time during the second CMP process based on the real time measurement of the planarity of the front-side surface of the work piece. For example, a pressure exerted by each pressure element in the second plurality of pressure elements may be adjusted in real time according to the real time measurement of the planarity of the front-side surface of the work piece during the second CMP process.

At act 818, in some embodiments, act 812 is repeated until the planarity of the front-side surface of the workpiece meets predetermined criteria. The repeated second CMP process(es) may, for example, be performed by the second CMP head, the first CMP head, or other CMP head(s) having another distribution(s) of pressure elements across the another CMP head(s) that is different from the first distribution and/or the second distribution. For example, act 812 may be repeated until a TTV of the front-side surface of the workpiece is about zero or otherwise less than a predetermined number (e.g., less than 0.30 um). In some embodiments, the repeated second CMP process(es) may be performed by, for example, the third CMP head 502 of FIG. 5 or 6 and/or the fourth CMP head 510 of FIG. 5 or 6.

FIGS. 9-14 illustrate cross-sectional views 900-1400 of some embodiments of structures illustrating the acts of the method 800 of FIG. 8. Although the cross-sectional views 900-1400 shown in FIGS. 9-14 are described with reference to a method, it will be appreciated that the structures shown in FIGS. 9-14 are not limited to the method but rather may stand alone separate of the method. Furthermore, although FIGS. 9-14 are described as a series of acts, it will be appreciated that these acts are not limiting in that the order of the acts can be altered in other embodiments, and the methods disclosed are also applicable to other structures. In other embodiments, some acts that are illustrated and/or described may be omitted in whole or in part. In addition, although the method is described in relation to the structures of FIGS. 9-14, it will be appreciated that the method is not limited to structures, but instead may stand alone.

FIG. 9 illustrates a cross-sectional view 900 corresponding to some embodiments of the act 802. As illustrated in FIG. 9, a workpiece 902 is provided. In some embodiments, the workpiece 902 includes a semiconductor structure 906 overlying a carrier substrate 904. In various embodiments, the semiconductor structure 906 may include an interconnect structure (not shown) disposed along a semiconductor substrate (not shown). In yet further embodiments, the workpiece 902 may, for example, be or comprise a semiconductor wafer supporting electronic circuits under manufacture. Further, a front-side surface 902 f of the workpiece 902 may, for example, be defined by a top surface of the semiconductor structure 906.

FIG. 10 illustrates a cross-sectional view 1000 corresponding to some embodiments of the act 804. As illustrated in FIG. 10, a thinning process is performed on the front-side surface 902 f of the workpiece 902. In some embodiments, the thinning process includes performing a mechanical grinding process into the top surface of the semiconductor structure 906, thereby reducing a thickness of the semiconductor structure 906 from an initial thickness Ti to a first thickness Ts1. In yet further embodiments, after performing the thinning process, a TTV of the workpiece 902 along the front-side surface 902 f may be substantially large (e.g., a TTV greater than about 0.35 um). Further, the front-side surface 902 f of the workpiece 902 may correspond to a to-be-polished surface of the workpiece 902.

FIG. 11 illustrates a cross-sectional view 1100 corresponding to some embodiments of the acts 806 and 808. As illustrated in FIG. 11, a first chemical mechanical polishing (CMP) process is performed on the front-side surface 902 f of the workpiece 902. In some embodiments, during the first CMP process, the workpiece 902 is arranged in a first CMP head 106 with the front-side surface 902 f (i.e., referred to as a to-be-polished surface of the workpiece 902) of the workpiece 902 facing down, and rotated about an axis of a CMP head spindle 430 coupling the first CMP head 106 to a motor. Further, the front-side surface 902 f of the workpiece 902 is pressed against a polishing pad 404. The polishing pad 404 is arranged over a platen 402 and rotated about an axis of a platen spindle 418 coupling the platen 402 to a motor.

With the dual-rotation of the polishing pad 404 and the workpiece 902, a slurry arm (406 of FIG. 4) provides slurry (411 of FIG. 4) to the polishing pad 404. The slurry may, for example, comprise abrasive and chemical components. Further, a first plurality of pressure elements 140 a-e are arranged proximate to the workpiece 902 and are configured to exert independent amounts of suction or pressure onto corresponding concentric regions of a back-side surface 902 b of the workpiece 902. The concentric regions of the back-side surface 902 b of the workpiece 902 correspond to the first plurality of concentric pressure zones A1-A5 distributed across the first CMP head 106. The suction or pressure applies force to the workpiece 902 such that the front-side surface 902 f of the workpiece 902 is pressed against the polishing pad 404. Due to the pressing force against the workpiece 902 and the abrasive components, the workpiece 902 undergoes mechanical polishing. Further, due to the chemical components of the slurry, the workpiece 902 also undergoes chemical polishing. In yet further embodiments, the first CMP head 106 has a first distribution of the first plurality of pressure elements 140 a-e across the first CMP head 106 and/or across the back-side surface 902 b of the workpiece 902.

In some embodiments, due to processing tool limitations, the pressure elements in the first plurality of pressure elements 140 a-e may not evenly distribute pressure across the corresponding concentric pressure zones A1-A5. For example, a pressure exerted by the first pressure element 140 a of the first CMP head 106 may be greater in a center region of the concentric pressure zone A1 than in a peripheral region of the concentric pressure zone A1 (e.g., near the circumferential edge of the first pressure element 140 a of the first CMP head 106). Thus, areas of the front-side surface 902 f of the workpiece 902 between adjacent concentric pressure zones A1-A5 may be subjected to more or less polishing depending on the applied pressure, such that those areas of the workpiece 902 have a different wafer thickness that is not desired.

Further, a surface measurement apparatus 120 is disposed on the platen 402 and/or the polishing pad 404, and the surface measurement apparatus 120 is configured to measure surface condition(s) of the workpiece 902 before, during, and/or after the first CMP process. For example, the surface measurement apparatus 120 is configured to measure a planarity of the front-side surface 902 f of the workpiece 902 to identify locations of uneven regions (i.e., regions with an undesired workpiece thickness, or regions having hillocks and/or valleys) on the front-side surface 902 f of the workpiece 902. The surface measurement apparatus 120 may, for example be configured to provide optical, electrical, thermal, pressure, and/or acoustical sensing. In some embodiments, as the surface measurement apparatus 120 measures the planarity of the front-side surface 902 f of the workpiece 902 during the first CMP process, a pressure exerted by each pressure element in the first plurality of pressure elements 140 a-e may be adjusted according to the planarity measurement to achieve a desired workpiece thickness.

FIG. 12 illustrates a cross-sectional view 1200 corresponding to some embodiments of the workpiece 902 after performing the act 806. As illustrated in FIG. 12, after performing the first CMP process, the thickness of the workpiece 902 is reduced from the first thickness Ts1 to a second thickness Ts2. In yet further embodiments, a planarity of the front-side surface 902 f of the workpiece 902 may be measured after performing the first CMP process. The planarity may, for example, be measured by a planarity detection system of a first polishing apparatus or by an external planarity tool. Further, the planarity may, for example, be measured using eddy currents, laser pulses, ultrasonic pulses, while light interferometry, or another suitable method.

FIG. 13 illustrates a cross-sectional view 1300 corresponding to some embodiments of the acts 810 and 812. As illustrated in FIG. 13, a second CMP process is performed on the front-side surface 902 f of the workpiece 902. In some embodiments, during the second CMP process, the workpiece 902 is arrange in a second CMP head 114 with the front-side surface 902 f of the workpiece 902 facing down, and rotated about an axis of a CMP head spindle 430 coupling the second CMP head 114 to a motor. Further, the front-side surface 902 f of the workpiece 902 is pressed against a polishing pad 404. The polishing pad 404 is arrange over a platen 402 and rotated about an axis of a platen spindle 418 coupling the platen 402 to a motor.

With the dual-rotation of the polishing pad 404 and the workpiece 902, a slurry arm (406 of FIG. 4) provides slurry (411 of FIG. 4) to the polishing pad 404. The slurry may, for example, comprise abrasive and chemical components. Further, a second plurality of pressure elements 144 a-e are arranged proximate to the workpiece 902 and are configured to exert independent amounts of suction or pressure onto corresponding concentric regions of a back-side surface 902 b of the workpiece 902. The concentric regions of the back-side surface 902 b of the workpiece 902 correspond to the second plurality of concentric pressure zones B1-B5 distributed across the second CMP head 114. The suction or pressure applies force to the workpiece 902 such that the front-side surface 902 f of the workpiece 902 is pressed against the polishing pad 404. Due to the pressing force against the workpiece 902 and the abrasive components, the workpiece 902 undergoes mechanical polishing. Further, due to the chemical components of the slurry, the workpiece 902 also undergoes chemical polishing. In some embodiments, the pressure of the second plurality of pressure elements 144 a-e during the second CMP process is adjusted according to the planarity measurement taken during and/or after the first CMP process to achieve the desired workpiece thickness.

The second CMP head 114 has a second distribution of the second plurality of pressure elements 144 a-e across the second CMP head 114 and/or across the back-side surface 902 b of the workpiece 902. In various embodiments, the second distribution is different from the first distribution. Further, when centers of the first CMP head (106 of FIG. 11) and the second CMP head 114 are aligned, pressure elements in the second plurality of pressure elements 144 a-d may overlap a corresponding area between adjacent pressure elements of the first plurality of pressure elements 140 a-e. Thus, in some embodiments, the second plurality of pressure elements 144 a-e may compensate for an undesired wafer thickness achieved in the areas of the front-side surface 902 f of the workpiece 902 that correspond to regions between adjacent concentric pressure zones of the first plurality of concentric pressure zones (A1-A5 of FIG. 11) during the first CMP process. This, in part, results in the workpiece 902 having a more accurate planarization, such that the TTV of the front-side surface 902 f of the workpiece 902 after the second CMP process may be substantially small (e.g., less than about 0.3 um). Thus, by virtue of the distribution of the second plurality of pressure elements 144 a-e being different from the distribution of the first plurality of pressure elements 140 a-e a uniform planarization may be achieved such that the workpiece 902 has the substantially small TTV. In yet further embodiments, the second CMP head 114 may be configured as illustrated and/or described in FIG. 6, in which the second CMP head 114 comprises seven pressure elements.

Further, a surface measurement apparatus 120 is disposed on the platen 402 and/or the polishing pad 404, and the surface measurement apparatus 120 is configured to remeasure surface condition(s) of the workpiece 902 before, during, and/or after the second CMP process. For example, the surface measurement apparatus 120 is configured to remeasure a planarity of the front-side surface 902 f of the workpiece 902 to identify locations of uneven regions (i.e., regions with an undesired workpiece thickness, or regions having hillocks and/or valleys) on the front-side surface 902 f of the workpiece 902. The surface measurement apparatus 120 may, for example be configured to provide optical, electrical, thermal, pressure, and/or acoustical sensing. In some embodiments, as the surface measurement apparatus 120 remeasures the planarity of the front-side surface 902 f of the workpiece 902 during the second CMP process, a pressure exerted by each pressure element in the second plurality of pressure elements 144 a-e may be adjusted according to the planarity measurement to achieve a desired workpiece thickness.

FIG. 14 illustrates a cross-sectional view 1400 corresponding to some embodiments of the workpiece 902 after performing the act 810. In yet further embodiments, a planarity of the front-side surface 902 f of the workpiece 902 may be remeasured after performing the second CMP process. The planarity may, for example, be remeasured by a planarity detection system of a first polishing apparatus or by an external planarity tool. Further, the planarity may, for example, be measured using eddy currents, laser pulses, ultrasonic pulses, while light interferometry, or another suitable method.

In some embodiments, in an effort to further increase the planarity of the front-side surface 902 f of the workpiece 902, one or more additional CMP process(es) may be performed on the workpiece 902 after the second CMP process. In an embodiment, after performing the second CMP process of FIG. 13, a third CMP process is performed on the front-side surface 902 f of the workpiece 902 by a third CMP head. In such embodiments, the third CMP head may be configured as the third CMP head 502 of FIG. 5 or 6 and the third CMP process may be performed by process(es) substantially similar to process(es) described above in FIG. 13. In another embodiment, after performing the second CMP process of FIG. 13, a third CMP process is performed on the front-side surface 902 f of the workpiece 902 by a third CMP head, and then a fourth CMP process is performed on the front-side surface 902 f of the workpiece 902 by a fourth CMP head. In such embodiments, the third CMP head may be configured as the third CMP head 502 of FIG. 5 or 6, the fourth CMP head may be configured as the fourth CMP head 510 of FIG. 5 or 6, and the third and fourth CMP processes may each be performed by process(es) substantially similar to process(es) described above in FIG. 13.

Accordingly, in some embodiments, the present disclosure relates to a CMP system comprising a first CMP head configured to perform a first CMP process on a workpiece and a second CMP head configured to perform a second CMP process on the workpiece after performing the first CMP process. A distribution of pressure elements across the second CMP head is different from a distribution of pressure elements across the first CMP head.

In some embodiments, the present application provides a chemical mechanical polishing (CMP) system including: a first CMP head configured to retain a workpiece, wherein the first CMP head includes a first plurality of pressure elements disposed across a first pressure control plate; and a second CMP head configured to retain the workpiece, wherein the second CMP head includes a second plurality of pressure elements disposed across a second pressure control plate, wherein a distribution of the first plurality of pressure elements across the first pressure control plate is different from a distribution of the second plurality of pressure elements across the second pressure control plate.

In some embodiments, the present application provides a polishing system for performing a polishing process including: a first polishing apparatus comprising a first platen and a first chemical mechanical polishing (CMP) head, wherein the first CMP head is configured to perform a first CMP process on a to-be-polished surface of a workpiece, wherein the first CMP head comprises a first plurality of concentric pressure elements and a first annular retaining ring laterally enclosing the first plurality of concentric pressure elements; a second polishing apparatus comprising a second platen and a second CMP head, wherein the second CMP head is configured to perform a second CMP process on the to-be-polished surface of the workpiece, wherein the second CMP head comprises a second plurality of concentric pressure elements and a second annular ring laterally enclosing the second plurality of concentric pressure elements, wherein widths of the second plurality of concentric pressure elements are respectively different from widths of the first plurality of concentric pressure elements; a surface measurement apparatus positioned on the first platen and the second platen, wherein the surface measurement apparatus is configured to measure a planarity of the to-be-polished surface of the workpiece in real time while performing the first and second CMP processes, wherein pressures exerted by the second plurality of concentric pressure elements during the second CMP process are based on the measured planarity of the to-be-polished surface after the first CMP process; and a transport apparatus configured to transport the workpiece between the first polishing apparatus and the second polishing apparatus.

In some embodiments, the present application provides a method for chemical mechanical polishing (CMP) of a workpiece, the method includes: performing a first CMP process on a front-side surface of the workpiece with a first CMP head having a first distribution of a first plurality of pressure elements across the first CMP head; measuring a planarity of the front-side surface of the workpiece; and performing a second CMP process on the front-side surface of the workpiece with a second CMP head having a second distribution of a second plurality of pressure elements across the second CMP head, wherein a pressure exerted by the second plurality of pressure elements is based on the measured planarity of the front-side surface of the workpiece, and wherein the second distribution is different from the first distribution.

The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure. 

What is claimed is:
 1. A chemical mechanical polishing (CMP) system comprising: a first CMP head configured to retain a workpiece, wherein the first CMP head comprises a first plurality of pressure elements disposed across a first pressure control plate; and a second CMP head configured to retain the workpiece, wherein the second CMP head comprises a second plurality of pressure elements disposed across a second pressure control plate, wherein a distribution of the first plurality of pressure elements across the first pressure control plate is different from a distribution of the second plurality of pressure elements across the second pressure control plate.
 2. The CMP system of claim 1, wherein the first plurality of pressure elements are respectively concentric with respect to one another and with respect to a center of the first pressure control plate, wherein the second plurality of pressure elements are respectively concentric with respect to one another and with respect to a center of the second pressure control plate.
 3. The CMP system of claim 1, wherein a number of pressure elements within the first plurality of pressure elements is equal to a number of pressure elements within the second plurality of pressure elements.
 4. The CMP system of claim 1, wherein a number of pressure elements within the first plurality of pressure elements is less than a number of pressure elements within the second plurality of pressure elements.
 5. The CMP system of claim 1, wherein a diameter of the first pressure control plate is equal to a diameter of the second pressure control plate.
 6. The CMP system of claim 1, wherein a diameter of an innermost pressure element of the first plurality of pressure elements is less than a diameter of an innermost pressure element of the second plurality of pressure elements.
 7. The CMP system of claim 1, wherein widths of the first plurality of pressure elements are respectively different from widths of the second plurality of pressure elements.
 8. The CMP system of claim 1, further comprising: a third CMP head configured to retain the workpiece, wherein the third CMP head comprises a third plurality of pressure elements disposed across a third pressure control plate, wherein a distribution of the third plurality of pressure elements across the third pressure control plate is different from the distribution of the first plurality of pressure elements and the distribution of the second plurality of pressure elements.
 9. The CMP system of claim 1, wherein the first and second plurality of pressure elements respectively comprise a concentric chamber configured to provide independent pressures to corresponding regions of the workpiece.
 10. A polishing system for performing a polishing process comprising: a first polishing apparatus comprising a first platen and a first chemical mechanical polishing (CMP) head, wherein the first CMP head is configured to perform a first CMP process on a to-be-polished surface of a workpiece, wherein the first CMP head comprises a first plurality of concentric pressure elements and a first annular retaining ring laterally enclosing the first plurality of concentric pressure elements; a second polishing apparatus comprising a second platen and a second CMP head, wherein the second CMP head is configured to perform a second CMP process on the to-be-polished surface of the workpiece, wherein the second CMP head comprises a second plurality of concentric pressure elements and a second annular ring laterally enclosing the second plurality of concentric pressure elements, wherein widths of the second plurality of concentric pressure elements are respectively different from widths of the first plurality of concentric pressure elements; a surface measurement apparatus positioned on the first platen and the second platen, wherein the surface measurement apparatus is configured to measure a planarity of the to-be-polished surface of the workpiece in real time while performing the first and second CMP processes, wherein pressures exerted by the second plurality of concentric pressure elements during the second CMP process are based on the measured planarity of the to-be-polished surface after the first CMP process; and a transport apparatus configured to transport the workpiece between the first polishing apparatus and the second polishing apparatus.
 11. The polishing system of claim 10, further comprising: a third polishing apparatus comprising a third platen and a third CMP head, wherein the third CMP head is configured to perform a third CMP process on the to-be-polished surface of the workpiece, wherein the third CMP head comprises a third plurality of concentric pressure elements and a third annular ring laterally enclosing the third plurality of concentric pressure elements, wherein widths of the third plurality of concentric pressure are respectively different from widths of the first and second plurality of concentric pressure elements.
 12. The polishing system of claim 11, wherein a width of an innermost concentric pressure element of the first CMP head is greater than widths of concentric pressure elements of the first CMP head that laterally surround the innermost concentric pressure element of the first CMP head, and wherein a width of an innermost concentric pressure element of the third CMP head is less than the width of the innermost concentric pressure element of the first CMP head.
 13. The polishing system of claim 12, wherein a width of a second innermost concentric pressure element of the third CMP head is greater than the width of the innermost concentric pressure element of the third CMP head.
 14. The polishing system of claim 11, wherein a number of concentric pressure elements within the first plurality of concentric pressure elements is less than a number of concentric pressure elements within the second plurality of concentric pressure elements, and a number of concentric pressure elements within the third plurality of concentric pressure elements is greater than the number of concentric pressure elements in the second plurality of concentric pressure elements.
 15. The polishing system of claim 11, further comprising: a forth polishing apparatus comprising a fourth platen and a fourth CMP head, wherein the fourth CMP head is configured to perform a fourth CMP process on the to-be-polished surface of the workpiece, wherein the fourth CMP head comprises a fourth plurality of concentric pressure elements and a fourth annular ring laterally enclosing the fourth plurality of concentric pressure elements, wherein widths of the fourth plurality of concentric pressure elements are respectively different from widths of the first, second, and third plurality of concentric pressure elements.
 16. The polishing system of claim 15, wherein the first, second, third, and fourth plurality of concentric pressure elements respectively comprise a same number of concentric pressure elements.
 17. A method for chemical mechanical polishing (CMP) of a workpiece, the method comprising: performing a first CMP process on a front-side surface of the workpiece with a first CMP head having a first distribution of a first plurality of pressure elements across the first CMP head; measuring a planarity of the front-side surface of the workpiece; and performing a second CMP process on the front-side surface of the workpiece with a second CMP head having a second distribution of a second plurality of pressure elements across the second CMP head, wherein a pressure exerted by the second plurality of pressure elements is based on the measured planarity of the front-side surface of the workpiece, and wherein the second distribution is different from the first distribution.
 18. The method of claim 17, wherein a width of an innermost pressure element of the first CMP head is less than a width of an innermost pressure element of the second CMP head.
 19. The method of claim 17, further comprising: performing a third CMP process on the front-side surface of the workpiece with a third CMP head having a third distribution of a third plurality of pressure elements across the third CMP head, wherein the third distribution is different from the first distribution and the second distribution.
 20. The method of claim 19, further comprising: performing a fourth CMP process on the front-side surface of the workpiece with a fourth CMP head having a fourth distribution of a fourth plurality of pressure elements across the fourth CMP head, wherein the fourth distribution is different from the first distribution, the second distribution, and the third distribution. 